Thermal insulating block



Jan. 9, 1962 e. H. SCHARPF THERMAL INSULATING BLOCK Filed March 25, 1959 INVENTOR.

65086,? H. 3C H/MPF BY Mia/4+7 075 Art r ie/5 United States Patent This invention relates to thermal insulating supports, and more particularly to those formed of metal.

A known insulating support for an object, to or from which it is desired to reduce heat transfer as much as possible, is a stack of thin metal plates. It has been found that such a stack formed from stainless steel plates 0.0008 inch thick and under a pressure of 1000 pounds per square inch will conduct heat at a rate only 2% of the rate of conduction of a stack having the same dimensions but formed of a solid block of metal. This surprising amount of thermal insulation is obtained because the contact resistance between the various plates acts as an insulator. An objection to such a thermal support is that it will support only compressive loads. If shear loads are applied to it, the plates will slide apart. Also, the whole stack of plates will fall apart if the longitudinal pressure on it is removed.

It is among the objects of this invention to provide a thermal insulating member which can be used to space apart two objects having difierent temperatures, which has great strength under compression, which is formed from two interlocking pieces of metal, and which is simple and inexpensive to make.

In accordance with this invention an insulating block is formed from two thin metal strips, each of which has been folded back and forth upon itself to form a stack of substantially parallel plates. The plates of the two stacks are alternately interleaved with one another, and one stack is turned 90 to the other'stack in order to lock the two stacks together. In use, the bock is compressed lengthwise of the stacks by the objects it spaces apart. This holds all of the plates in contact with one another.

The preferred embodiment of the invention is illustrated in the accompanying drawing, in which:

FIG. 1 is a section through two concentric vessels having different temperatures, showing my insulating blocks in elevation; and

FIG. 2 is an enlarged fragmentary perspective view of one of the blocks with the two strips partly unfolded.

Referring to FIG. 1 of the drawing, my thermal insuating blocks can be used wherever the supporting members that space two objects apart must conduct as little heat as possible from one to the other. For example, a vacuum flask containing liquid oxygen and composed of inner and outer vessels or shells 1 and 2 may use my insulating supports 3 between the shells to support the inner one and space it from the outer shell. Another use is for spacing a hot inner shell or casing from an outer casing, such as in a jet engine or the like. When the two shells or casings are circular, the supports are disposed radially thereof and span the space between them.

Each support is in the form of a block or bar and is formed from two long, narrow, metal strips 4 and 5 that may be extremely thin. As shown in FIG. 2, each strip is folded back and forth upon itself to form a stack of substantially parallel plates 6. For best results the folds should be so spaced that each plate will be approximately square. The folding of the strips is done in such a way that the plates of the two stacks will be alternately interleaved and with one stack turned on its longitudinal axis 90 to the other. This arrangement locks the two stacks together so that they can be separated neither laterally nor longitudinally.

3,016,160 Patented Jan. 9, 1962 As shown in FIG. 2, each spacing member or block is formed by placing the two metal strips at right angles to each other with one end of strip 4 overlapping an end of strip 5. The latter then is folded around one edge of strip 4 and back across the overlapping end of that strip, and then the first strip 4 is folded across the portion of the second strip that was just extended across the first strip. This alternate folding of the strips back and forth across one another proceeds until there is no more material to fold. It is preferred to use strips of equal length, whereby one end of the resulting stack will be formed from the end plate of one strip and the opposite end of the stack E'Wlll be formed from the end plate of the other strip.

. Although the folds in the two strips are made as sharp aspossible, the various plates 6 ordinarily will not lie flat against each other because of the tendency of the strips to straighten out. However, the supports are made in such length that before they can be mounted in place between the two shells that they separate, they must be compressed lengthwise in order to insert them. This compression is necessary in order to hold the inner shell firmly in position within the outer shell. In other words, the spacers should and do act like solid blocks or posts as far as their supporting properties are concerned. They may be held in place in various ways, a preferred way being to fit their ends into rectangular openings in washers 7 secured to the two shells. In such a case, the washers may be fitted over the ends of a block and then the entire unit inserted between the shells, followed by welding the washers to the shels. Due to the compression of the blocks, their individual plates will be held in contact with one another throughout their areas. Nevertheless, a surprising thing about the spacer is that the contact resistance between the numerous plates is so great that the block is an extremely poor conductor of heat. Its insulating properties are not affected noticeably by the fact that the plates are integrally connected end to end.

Becauseof the manner in which the two stacks of plates are interconnected, it will be seen that neither stack can move laterally away from the other. Therefore, the block will take shear loads successfully. By having all of the plates in each stack integrally connected and the plates of the two stacks alternately interleaved, the block is self-supporting and will not fall apart when not under compression. Consequently, it is much easier to handle than a stack of separate, individual plates.

Although it has been assumed herein that clean metal strips are used, it is possible to reduce heat transfer even more by coating the strips with fine dust particles so that there will be extremely thin layers of dust between the plates in the block.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

The combination with a pair of adjacent objects having different temperatures, of rigid spacing blocks extending across the space between said objects, each block comprising two thin metal strips each folded back and forth upon itself to form a stack of parallel plates spaced apart a distance equal to their individual thickness, and the plates of the two stacks being alternately-interleaved but with one stack turned to the other stack to lock the 3 stacks together, said blocks being tightly compressed lengthwise of said stacks by said objects to press said plates tightly against one another throughout their areas to rigidly support one of said objects from the other in fixed spaced relation thereto, and the blocks thermally insulat- 5 ing each of said objects from the other.

UNITED STATES PATENTS Robinsohn Apr. 15, 1902 Brown June 12, 1906 Gleason Nov. 16, 1926 Dexter Aug. 18, 1931 

